The process of metastasis, the dissemination of tumor cells to sites in the body distant from the original site of the tumor, often involves invasion of blood vessels by the tumor cells. The blood vessel wall includes a dense extracellular matrix (ECM) of connective tissue that must be penetrated by any cell entering or leaving the vessel. The ECM includes a proteoglycan scaffold that constitutes a physical barrier to cell penetration.
It was found by the research groups of Vlodavsky (Vlodavsky, J. Fuks, Z. and Schirrmacher, V. In: The Endothelial Cell--A Pluripotent Cell of the Vessel Wall. Eds. Thilo-Korner, D.G.S. and Fresney, R.I., Basel: Karger, pp. 126-157, 1983; Vlodavsky, I., Fuks, Z., Bar-Ner, M, and Schirrmacher, V. Cancer Res. 43: 2704, 1983) and of Nicolson (Nakajima, M. Irimura, T., DiFerrante, D., Ferrante, N. and Nicolson, G.L. Science 220: 611, 1983) that tumor cells that were highly metastatic expressed an enzyme, heparanase, that attacked the heparan sulfate moiety of the ECM proteoglycans. Tumor cells that were less metastatic expressed less heparanase enzyme. Heparanase activity was also associated with the capacity of non-tumor cells such as T lymphocytes to move through blood vessels.
In view of the above, we have considered the possibility that inhibitors of heparanse enzyme activity might handicap the movements of cells into and out of blood vessels, thereby obstructing the metastasis of tumor cells leading to prolongation of life. Experiments in this direction have confirmed that positive results can be obtained, as set out in the following.